Comparing Complication Rates, Costs, and Length of Stay between Unicompartmental and Total Knee Arthroplasty: Insights from a Big Data Analysis Using the NIS Dataset

Abstract

Introduction: Unicompartmental knee arthroplasty (UKA) is gaining traction as a treatment for knee osteoarthritis due to faster recovery, better range of motion, and reduced healthcare costs compared to total knee arthroplasty (TKA). UKA preserves healthy parts of the knee, leading to a quicker return to function and less pain. However, TKA offers potentially longer-lasting results with lower revision rates. This study investigates the National Inpatient Sample (NIS) database for UKA and TKA patients to understand their relative benefits and limitations, aiming to inform patient care and resource allocation. Methods: This retrospective analysis examined outcomes following UKA and TKA using the Nationwide Inpatient Sample (NIS) database (2016-2019). Patients undergoing elective UKA or TKA (n=2,606,925) were identified using ICD-10 codes (Appendix). To minimize confounding factors, propensity score matching was performed using patient demographics, hospital characteristics, and comorbidities, resulting in a balanced cohort of 136,890 patients. In-hospital mortality, length of stay, postoperative complications, and hospitalization costs were compared (p < 0.05). This study received exempt IRB approval due to de-identified data. Results: The prevalence of UKA procedures significantly increased over the study period, with primary osteoarthritis being the leading cause for both UKA and TKA. Patients undergoing UKA were younger and had less comorbidities compared to those undergoing TKA. Propensity score matching effectively balanced these baseline characteristics between the two groups. Examining hospitalization outcomes in propensity-matched cohorts revealed low in-hospital mortality for both groups (0.015%). However, UKA demonstrated a clear advantage in terms of shorter length of stay (1.53 days vs. 2.47 days) and lower total hospitalization charges ($55,976 vs. $61,513). While UKA had slightly higher rates of intraoperative fracture and pulmonary edema compared to TKA, TKA was associated with a significantly increased risk of various complications. These included blood transfusion, blood loss anemia, acute coronary artery disease, pulmonary embolism, pneumonia, and acute kidney injury. Conclusion: UKA shows promise as a less-invasive option for younger patients with one-sided knee osteoarthritis, potentially offering shorter hospital stays, lower costs, and potentially fewer complications.